The sound of a lawn mower humming to life on a warm spring day is music to the ears of any homeowner. But when that hum turns into a sputtering cough, or worse, silence, a sense of dread can quickly settle in. A faulty ignition coil is a common culprit behind these frustrating lawn mower woes. Fortunately, diagnosing this issue is within reach, even for the novice mechanic, with the help of a trusty multimeter. This guide will walk you through the process of checking your lawn mower coil using a multimeter, equipping you with the knowledge to troubleshoot and fix your mower with confidence.
In a Nutshell
A lawn mower’s ignition coil is responsible for converting the low voltage from the battery into a high voltage spark that ignites the fuel mixture in the engine. To check the coil with a multimeter, you’ll be measuring its resistance across different terminals. By comparing these readings to the specifications provided by the manufacturer, you can determine whether the coil is faulty.
Understanding the Ignition Coil and Its Function
Before diving into the testing procedure, let’s understand the role of the ignition coil in your lawn mower’s engine. The coil itself is a simple device, but it plays a crucial role in the combustion process:
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Receiving Low Voltage: The ignition coil receives low voltage from the battery, typically around 12 volts.
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Stepping Up the Voltage: Within the coil, a magnetic field is created and then interrupted, inducing a high-voltage pulse in the coil’s secondary winding. This voltage can reach thousands of volts.
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Delivering Spark to the Spark Plug: The high-voltage pulse is then directed to the spark plug, causing a spark to jump across the gap in the spark plug. This spark ignites the fuel-air mixture in the combustion chamber, powering the engine.
Gathering Your Tools and Materials
To test your lawn mower coil, you’ll need a few basic tools:
- Multimeter: This is the most essential tool for testing the coil’s resistance. Make sure you have a multimeter that can measure resistance (ohms).
- Lawn Mower Manual: This document provides the specific resistance specifications for your coil, allowing you to compare your measurements to the manufacturer’s guidelines.
- Safety Glasses: Protect your eyes from any potential debris or sparks while working on the lawn mower.
Testing the Ignition Coil Using a Multimeter
Now that you’ve gathered your tools, it’s time to test the ignition coil. Follow these steps carefully:
1. Disconnect the Ignition Coil
- Locate the Ignition Coil: The ignition coil is usually a small black or brown box, typically located near the spark plug and attached to the engine block.
- Disconnect the Wires: Carefully disconnect the wire leading from the coil to the spark plug, and any other wires connected to the coil (e.g., the ignition switch wire).
2. Set Your Multimeter to Resistance Mode
- Select the ‘Ohms’ Setting: On your multimeter, turn the dial to the ohms (Ω) setting.
3. Measure Resistance Across the Primary Winding
- Identify the Primary Terminals: The ignition coil typically has two main terminals: the primary terminal and the secondary terminal. The primary terminal is often connected to a wire that runs to the ignition switch.
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Connect the Multimeter Leads: Connect one lead of your multimeter to the primary terminal and the other lead to the coil case (the metal body of the coil).
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Record the Reading: Note the resistance reading displayed on your multimeter.
4. Measure Resistance Across the Secondary Winding
- Identify the Secondary Terminal: The secondary terminal is usually connected to a wire leading to the spark plug.
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Connect the Multimeter Leads: Connect one lead of your multimeter to the secondary terminal and the other lead to the coil case.
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Record the Reading: Note the resistance reading displayed on your multimeter.
5. Compare Readings to Manufacturer Specifications
- Consult Your Lawn Mower Manual: Refer to your lawn mower’s owner’s manual to find the specified resistance values for your coil’s primary and secondary windings.
- Analyze the Results: Compare your measured resistance values to the manufacturer’s specifications. If the readings are significantly different from the specified values, the coil is likely faulty and needs to be replaced.
Troubleshooting Common Problems and Interpreting Test Results
Now that you’ve tested the coil, let’s interpret the results and troubleshoot potential problems:
1. Open Circuit:
- What it means: If the multimeter displays an “OL” (over limit) or a very high resistance value, it indicates an open circuit in the coil’s winding.
- Troubleshooting: An open circuit means the coil has a break in its wire, preventing current flow. A faulty coil needs to be replaced.
2. Short Circuit:
- What it means: If the multimeter displays a very low resistance value, it indicates a short circuit within the coil’s winding.
- Troubleshooting: A short circuit occurs when the windings in the coil touch each other, creating an unintended path for current to flow. A faulty coil needs to be replaced.
3. Resistance Out of Range:
- What it means: If the measured resistance values fall outside the manufacturer’s specified range, it’s a strong indication that the coil is faulty.
- Troubleshooting: A coil with resistance outside the specified range might not be able to generate enough spark to ignite the fuel mixture efficiently. The coil should be replaced.
Tips for Maintaining Your Lawn Mower Coil
To extend the life of your lawn mower coil, follow these maintenance tips:
- Keep the Coil Clean: Dust and debris can accumulate on the coil, affecting its performance. Regularly clean the coil with a dry cloth or compressed air.
- Inspect the Wires: Check the wires leading to and from the coil for signs of damage, such as cracks, frays, or corrosion. Replace damaged wires promptly.
- Avoid Moisture: The ignition coil is sensitive to moisture. Store your lawn mower in a dry place to prevent moisture buildup.
Conclusion
Testing your lawn mower coil with a multimeter is a simple and effective way to diagnose ignition problems. By following the steps outlined in this guide, you can accurately determine whether your coil needs to be replaced. Remember to always consult your lawn mower’s manual for specific resistance values and troubleshooting advice. With a little knowledge and a multimeter, you can keep your lawn mower running smoothly for years to come.
FAQs
What is a lawn mower coil and what does it do?
The lawn mower coil is a crucial component of the ignition system. It’s a small, cylindrical device with copper windings wrapped around a core. When the ignition switch is turned on, the coil receives electrical energy from the battery and transforms it into high voltage. This high voltage is then sent to the spark plug, creating a spark that ignites the fuel-air mixture in the engine.
Without a functioning coil, your lawnmower won’t be able to start. This is because it won’t generate the spark needed to ignite the fuel. A faulty coil can cause several problems, including a lack of power, difficulty starting, or even a complete failure to start.
How can I tell if my lawn mower coil is dead?
You can tell if your lawn mower coil is dead by checking for symptoms like difficulty starting, misfiring, or a complete lack of power. You can also use a multimeter to test the coil’s resistance. A faulty coil will have a different resistance reading than a healthy coil.
If you suspect your coil is dead, it’s important to test it before replacing it. You can use a multimeter to measure the resistance of the coil and compare it to the manufacturer’s specifications. If the resistance is out of range, then the coil is likely dead.
How do I use a multimeter to test my lawn mower coil?
To test your lawn mower coil with a multimeter, you will need to set the multimeter to the resistance setting (usually symbolized by an ohm symbol). Then, touch the multimeter’s probes to the two terminals of the coil. The multimeter will display a reading, which should be within the manufacturer’s specifications for your specific model.
If the multimeter displays a reading that is outside of the manufacturer’s specifications, it indicates that the coil is faulty and needs to be replaced. Remember to always consult your lawnmower’s manual for the specific resistance values for your coil.
What are the common causes of a dead lawn mower coil?
There are a few common causes of a dead lawn mower coil. One of the main causes is age. Over time, the insulation on the coil’s wires can degrade, leading to short circuits or open circuits. Another common cause is exposure to heat. The coil can overheat if the engine is running too hot, which can damage the coil’s windings.
Finally, moisture can also damage the coil. If the coil is exposed to water or humidity, it can cause corrosion or short circuits. To prevent coil failure, it is essential to maintain your lawnmower regularly and ensure proper airflow to keep the engine cool.
How much does a new lawn mower coil cost?
The cost of a new lawn mower coil can vary depending on the make and model of your lawnmower. Generally, you can expect to pay between $20 and $50 for a replacement coil. However, it’s always a good idea to check with your local lawnmower repair shop or online retailers to get the most accurate price.
If you are comfortable working with tools and electrical components, you can replace the coil yourself. Otherwise, you can take your lawnmower to a qualified mechanic for repair.
What are some tips for preventing a lawn mower coil from going bad?
Preventing a lawn mower coil from going bad involves proper maintenance and care. First, ensure you always use the correct type of gasoline and oil for your lawnmower. Second, regularly clean your lawnmower’s air filter to ensure proper airflow and prevent engine overheating.
Third, inspect your lawnmower’s spark plug regularly and replace it as needed. A worn-out spark plug can cause increased wear on the coil. Lastly, store your lawnmower in a dry and cool place to minimize moisture exposure, which can damage the coil.
What should I do if my lawn mower coil is dead?
If you’ve determined that your lawn mower coil is dead, you have two options: replace it yourself or take it to a repair shop. Replacing a lawn mower coil is relatively simple, and many online resources and tutorials can guide you. However, if you’re not comfortable working with electrical components, it’s best to take your lawnmower to a professional.
Replacing the coil yourself can save you money but be sure to have the correct replacement part for your specific lawnmower model. Ensure you follow all safety precautions when working with electrical components. If you take it to a repair shop, the cost will vary depending on the labor and parts.